PROJECT SUMMARY With aging, the sagittal convexity of the normal thoracic spine tends to progress. Hyperkyphosis is a pathological accentuation of this process, commonly known as the "dowager's hump." Studies have shown that hyperkyphosis affects as many as 20% to 40% of older adults, making it a serious public health concern. Until recently, most have assumed that hyperkyphosis affects predominantly older women. Part of this assumption stems from the misconception that hyperkyphosis equals spine osteoporosis;however, studies demonstrate that more than half of those with the worst degrees of kyphosis don't have underlying vertebral fractures. In addition, several observational studies suggest that older men are at least as affected by age- related changes in posture as older women, and that compared to women, hyperkyphotic men may even be at greater risk of adverse health outcomes such as injurious falls and increased mortality. Given these intriguing findings that suggest clear sex differences in age-related posture that may have different and significant health related implications, further investigation of hyperkyphosis in men is warranted. To address the challenge of better identifying male hyperkyphosis and understanding its epidemiology in terms of pathogenesis and health outcomes, Dr. Kado has assembled an expert team to leverage a powerful resource, the existing comprehensive data set from the Osteoporotic Fractures in Men (MrOS) Study. MrOS is the first and largest prospective U.S. study devoted primarily to the investigation of osteoporotic fractures in men. Dr. Kado and colleagues propose to measure thoracic kyphosis in 1,000 older men from existing baseline and follow-up lateral spine radiographs an average of 4.6 years later to 1) determine how much of their hyperkyphosis is due to underlying osteoporosis and how much is related to other potential risk factors such as genetic predisposition, muscle weakness, intervertebral height loss, and health behaviors;2) determine what degree of kyphosis is associated with adverse outcomes such as falls, fractures, and functional limitations;and 3) compare and contrast three different measures of cervico-thoracic spinal curvature to determine the measure that best predicts important health consequences. If funded, they plan to identify the causes and consequences of hyperkyphosis in men, thus providing a solid foundation for understanding new diagnostic and therapeutic approaches towards this common and debilitating geriatric syndrome